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Stock-Based Compensation - Summary of Restricted Stock Activity (Detail)
shares in Thousands
3 Months Ended
Mar. 31, 2021
$ / shares
shares
2016 Employee Stock Purchase Plan  
Weighted Average  
Percentage of purchase limit on gross compensation 20.00%
Restricted Stock  
Number of Shares  
Unvested, Beginning balance (in shares) | shares 1,886
Granted (in shares) | shares 14
Vested (in shares) | shares (158)
Forfeited (in shares) | shares (112)
Unvested, Ending balance (in shares) | shares 1,630
Weighted Average  
Unvested, Beginning balance (in dollars per share) | $ / shares $ 5.14
Granted (in dollars per share) | $ / shares 3.07
Vested (in dollars per share) | $ / shares 9.73
Forfeited (in dollars per share) | $ / shares 6.58
Unvested, Ending balance (in dollars per share) | $ / shares $ 3.73